Abstract
The resonant shells of vibratory cylinder gyroscopes are commonly packaged in metallic caps. In order to lower the production cost, a portion of vibratory cylinder gyroscopes do not employ vacuum packaging. However, under non-vacuum packaging conditions there can be internal acoustic noise leading to considerable acoustic pressure which is exerted on the resonant shell. Based on the theory of the structural-acoustic coupling, the dynamical behavior of the resonant shell under acoustic pressure is presented in this paper. A finite element (FE) model is introduced to quantitatively analyze the effect of the structural-acoustic coupling. Several main factors, such as sealing cap sizes and degree of vacuum which directly affect the vibration of the resonant shell, are studied. The results indicate that the vibration amplitude and the operating frequency of the resonant shell will be changed when the effect of structural-acoustic coupling is taken into account. In addition, an experiment was set up to study the effect of structural-acoustic coupling on the sensitivity of the gyroscope. A 32.4 mV/°/s increase of the scale factor and a 6.2 Hz variation of the operating frequency were observed when the radial gap size between the resonant shell and the sealing cap was changed from 0.5 mm to 20 mm.
Highlights
The operation of vibratory cylinder gyroscopes relies on their symmetrical resonant shells which vibrate in a standing wave mode [1], it is necessary to provide a relatively stable package for the vibration of the resonant shells
It has been known that when the vibratory cylinder gyroscope rotates at an angular velocity, the sensing mode of the resonant shell begins to appear, and it is oriented at 45°relative to the exciting mode
Considering that the gyroscopes studied in this paper is a type of low cost cylinder gyroscopes without vacuum treatment, the major factor affecting the sensitivity of the gyroscope is the size of the sealing cap
Summary
The operation of vibratory cylinder gyroscopes relies on their symmetrical resonant shells which vibrate in a standing wave mode [1], it is necessary to provide a relatively stable package for the vibration of the resonant shells. It is considered that when the resonant shell vibrates at the operating frequency, there can be acoustic waves leading to considerable acoustic pressure inside the sealing cap [9]. The acoustic energy will affect the vibration of the resonant shell after reflecting back from the inner surface of the sealing cap. This phenomenon, known as structural-acoustic coupling, has received much attention in various fields. The structural-acoustic coupling effect on a type of low cost vibratory cylinder gyroscope without vacuum packaging is studied. Experiments were implemented to study the mechanical sensitivity (scale factor) of the gyroscope which could be affected by the structural-acoustic coupling effect. The simulation and experimental results are useful for a deeper understanding of the performance of the vibratory cylinder gyroscopes without vacuum packaging
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